1. Field of the Invention
The present invention relates to techniques for receiving a container for storing semiconductor substrates (or wafers), glass substrates for LCD devices, glass substrates for photomasks, substrates for optical disks (hereinafter referred to as “substrates”), and for transporting the substrates into and out of the container.
2. Description of the Background Art
Conventionally, unprocessed substrates stored in carriers are transported from outside into a substrate processing apparatus for performing a surface preparation such as an etching process on substrates. The carriers include an OC (open cassette) of the type wherein part of the container thereof is open to the outer atmosphere, and a FOUP (front opening unified pod) of the type wherein the container thereof is enclosed or sealed.
When the FOUP-type cassette (referred to simply as a “FOUP” hereinafter) is used to transport substrates between apparatuses, the substrates are transported while being enclosed in the FOUP. Thus, the cleanliness of the substrates is maintained even if particles and the like are present in the ambient atmosphere. This eliminates the need to make so high the cleanliness in a cleanroom in which the substrate processing apparatus is installed, to reduce costs required for the cleanroom.
Such a FOUP is received in a purpose-built substrate transfer apparatus incorporated in the substrate processing apparatus. At the substrate transfer apparatus, unprocessed substrate are removed out of the FOUP into the substrate processing apparatus, and processed substrates are collected into the FOUP. FIG. 10 is a perspective view of the conventional substrate transfer apparatus for the FOUP.
The substrate transfer apparatus 101 is incorporated as a loader in a substrate processing apparatus 100, and has the functions of receiving the FOUP with unprocessed substrates stored therein, and loading the substrates from the FOUP into the substrate processing apparatus 100. The substrate transfer apparatus 101 comprises a plurality of shelves 111, a transport robot 120, a holding table 130, and a lifter 140.
Each of the shelves 111 can receive one FOUP thereon. The FOUP transported from outside the substrate processing apparatus 100 into the substrate transfer apparatus 101 is received on one of the plurality of shelves 111.
The holding table 130 can place and hold one FOUP thereon. By opening the FOUP placed on the holding table 130, unprocessed substrates are removed out of the FOUP and loaded into the main body of the substrate processing apparatus 100.
The transport robot 120 includes a transport arm 121, and is capable of moving along the width of the substrate processing apparatus 100. The transport arm 121 is vertically movable with respect to the transport robot 120. Thus, the transport robot 120 enables the transport arm 121 to gain access to the holding table 130 and each of the plurality of shelves 111. The transport robot 120 transports the FOUP with unprocessed substrates stored therein from one of the plurality of shelves 111 to the holding table 130, and transports the empty FOUP out of which the substrates are removed from the holding table 130 to one of the plurality of shelves 111.
When the transport robot 120 transports the FOUP, the transport arm 121 supports the bottom portion of the FOUP from beneath. This is because transporting the FOUP suspended by the transport robot 120 which grasps a flange provided on the top portion of the FOUP does not allow quick increase and reduction in transport speed of the FOUP in terms of the strength of the flange, and accordingly does not allow high-speed transport of the FOUP.
Unfortunately, when the transport arm 121 supports the bottom portion of the FOUP, it is impossible to for the transport arm 121 to place the FOUP directly onto the holding table 130. For this reason, the FOUP supported from beneath by the transport arm 121 is temporarily transferred to the lifter 140 in the background art technique. The lifter 140 can grasp the flange provided on the top portion of the FOUP to hold the FOUP suspended thereby. The lifter 140 is movable up and down in the vertical direction over the holding table 130. Thus, after receiving the FOUP from the transport robot 120, the lifter 140 waits until the transport robot 120 moves to cause the transport arm 121 to shunt out of the space between the FOUP and the holding table 130, and then moves the FOUP held by the lifter 140 downwardly to place the FOUP on the holding table 130. Thereafter, the FOUP placed on the holding table 130 is opened, and unprocessed substrates are removed out of the FOUP and loaded into the main body of the substrate processing apparatus 100.
The above-mentioned procedure is reversed for the transport of an empty FOUP out of which substrates are removed from the holding table 130 to one of the shelves 111. Specifically, after the lifter 140 temporarily holds and lifts the empty FOUP, the transport robot 120 gains access to the holding table 130, and the FOUP is transferred from the lifter 140 to the transport arm 121 of the transport robot 120. Then, the lifter 140 releases the grasp of the FOUP, and the transport robot 120 to which the FOUP is transferred gains access to one of the shelves 111.
In the background art technique, as described above, it is impossible for the transport robot 120 to place the FOUP directly onto the holding table 130 and to receive the FOUP directly from the holding table 130. Thus, the transfer of the FOUP between the transport robot 120 and the holding table 130 must be carried out temporarily via the lifter 140. Therefore, the transfer of the FOUP between the transport robot 120 and the holding table 130 requires time for the lifter 140 to operate and time for the transport robot 120 to shunt, resulting in decrease in throughput.